Before buying any parts, it would be wise to get a build sheet from the local IHC dealer. Usually with no charge, using the bus ID number. I have a BB with a 7.3 and allison trans. I just bought some different gears for my bus. My bus has a 411 and I bought some 373 gears. The gears are not yet installed as I may have gone too high a ratio for the power available. I just returned from a 2500 mile trip and lost a coolant hose resulting in a broken head gasket. The last 125 miles were on a hook. I guess I expected too much from 125HP. Now there are lots of new decisions to make
The least expensive method changing rear gears is simply buying new gears, about $600, buying a used rear gear set attached to a carrier, or the complete rear axle assembly. First decide what is needed then begin the search. Heavy items are easier to go get the parts. Shipping is very spendy/pricey. Frank

looking for a rear end in 3.73 . i have a 1999 international t444e 36 footer thomas built. has a 4.44 spicer rear hydraulic brakes

It will be helpful to know which axle you have - and if all you want to do is change the gear ratio (and assuming your axle has no other problems) it will be far cheaper and easier to simply swap the carrier assembly, rather then the whole axle.

Mine being an '01 IH, it has an N175 axle (N190 is another common option).